I was notified about JBIDE-21745. I downloaded JBDS and created a Red Hat account on the developers.redhat.com registration site. The account is created, however it has a different user name than the e-mail I provided .

This is the reason why JBIDE-21745, because user then tries to enter the e-mail as its user name and it does not work, because the credentials do not match. I back traced the account in Keycloak and used the newly generated name and with it DM authenticates properly.